Genetic Changes in Hatchery Stocks of Brown Trout (Salmo trutta)

Abstract

Preservation of the genetic characteristics of a population is one of the primary objectives of many fish stocking programs. Using starch gel electrophoresis we have tested for temporal gene frequency stability at two polymorphic loci coding for α-glycerophosphate dehydrogenase and creatine phosphokinase. Three Swedish hatchery stocks of brown trout (Salmo trutta) and field samples from natural populations corresponding to two of these stocks were analyzed. Highly significant allele frequency changes at both loci indicated considerable lack of intra-stock genetic homogeneity. In the light of these findings we emphasize the importance of using large numbers of actual as well as effective parents to avoid inadvertent genetic changes and inbreeding. No stock should be founded or perpetuated using less than approximately 30 parents of the least numerous sex in any generation.Key words: inbreeding, genetic drift, gene bank, electrophoresis, stocking, trout